1. Field of the Invention
The present invention relates to method and apparatus of recording and reproducing picture information on and from a recording medium such as a video disc, a digital audio disc, and so on.
2. Description of Background Information
A system is proposed in which picture information is recorded and reproduced in the form of the subcode on and from a digital audio disc having a diameter of 12 cm, generally called compact disc (abbreviated as CD hereinafter). The subcode is made up of eight subcode bits, and bit groups forming the subcode are divided into eight channels denoted by letters P, Q, R, S, T, U, V, and W respectively. In the method in which the picture information is recorded and reproduced in the form of the subcode, data corresponding to picture information is configured such that a symbol is formed by 6 bits of channels R through W from among the 8 bits forming the subcode, and 98 symbols are treated as one block, as illustrated in FIG. 1. Two symbols in the 98 symbols are used as a sync signal, and 24 symbols obtained by dividing the remaining 96 symbols by four are treated as a minimum unit of data, i.e. a "pack", which constitutes one instruction of the picture processing.
More specifically, the first symbol (referred to as symbol 0 hereinafter) of the 24 symbols shows one of several modes. A symbol 1 following this symbol 0 forms "instruction" which indicates the sort of the instruction. Symbols 2 and 3 following the symbol 1 constitute a parity Q which is an error correction code. Symbols 4 through 19 following the parity Q constitute a data field, and include information such as color information. Finally, symbols 20 through 23 following the data field constitute a parity P which is an error correction code for protecting the information in the "pack".
On the other hand, there are four modes, i.e. "zero mode", "line-graphics mode", "TV-graphics mode", and "user's mode". The "zero mode" is provided for a case where no operation is required for pictures on the display screen, that is, picture are to be maintained as they are, and all data in the "pack" are 0 for this mode.
The "line-graphics mode" is provided for such a case that a liquid crystal display is provided on the front face of the player, to display notes such as an explanation of a music selection. As shown in FIG. 2, a picture area elongated sideways is formed by pixels which are arranged in 288 columns and 24 rows. In other words, each row includes 288 pixels and each column includes 24 pixels. The term "pixel" means the minimum display element of a picture, and it is general that the picture processing is performed by using picture composing units designated as "fonts" each of which is made up of pixels divided into 6 columns and 12 rows.
The number of "fonts" which can be displayed in the "line-graphics mode" is 48 in the lateral direction, and 2 in the column direction, and this area is designated as "screen area". For providing the scroll function, a line of "fonts" is added to the upper and lower outer peripheries and the right and left peripheries of the "screen area", to form a picture area having 50 "fonts" in the row direction, and 4 "fonts" in the column direction. The subcode is formed so that the picture processing is performed by using a memory having addresses each corresponding to each pixel in this picture area. In addition, the area outside the "screen area" is designated as "border".
The "TV-graphics mode" is a mode for displaying images on the TV screen, and a picture is formed by pixels arranged in 192 rows and 288 columns as illustrated in FIG. 3. The number of "fonts" which can be displayed in the "TV-graphics mode" is 48 in the direction of row, and 16 in the direction of column. Also in this "TV-graphics mode", the subcode is formed so that the picture processing is performed by using a memory having addresses each of which corresponds to each pixel in a picture area having 50 "fonts" in the direction of row, and 18 "fonts" in the direction of column, made by adding a line of "fonts" to the upper and lower peripheries as well as the right and left outer peripheries of the "screen area".
As instructions for the picture processing, there are an instruction for painting out the whole picture area by one certain color, an instruction for drawing a picture in one "font" on the screen by using two different colors, an instruction for moving the whole picture upward, downward, or sideways, and so on.
Additionally, in the 8-bit groups forming the subcode, the Q bits forming the channel Q include time information corresponding to the track length to a certain position of each information data which is recorded from the beginning of the program area of CD, and form address time data which can be used as positional data representing the recording position. On the other hand, the P bits forming the channel P provide data including information relating to a pause between two music selections.
In the above-described system of recording and reproducing picture information as subcode, the time period necessary for displaying a picture of one "font" is about 3.3/1000 second, and about 2.5 seconds are necessary for displaying 48.times.16 characters.
This means it is not possible to record and reproduce pictures with motion. Furthermore, since the maximum number of colors which can be used in one picture is not more than 16, there has been a drawback that the reproduced pictures obtained by the system explained so far are monotonous, or without variety.
Therefore, it is conceivable to produce a picture having variety by mixing a signal corresponding to the video information recorded as the subcode with a separately generated video format signal. In that case, however, a sense of incompatibility would be generated from the reproduced picture obtained by the mixing operation if there is no correlation between the picture information recorded as the subcode and the separately generated video signal. Therefore, it becomes necessary, for example, to adjust the timing of generation of the signal corresponding to the picture information recorded as the subcode and the video format signal by a manual operation. Thus, it has been difficult to obtain reproduced pictures with full of variety which do not generate the sense of incompatibility.